1. Technical Field
The technology relates to a filter medium and methods of use for cleaning metal-working liquids, and more particularly to metal-working liquids that are used in the manufacture of aluminum products such as sheets, foils and containers, such as beverage cans.
2. Description of the Related Art
It is commonplace to continuously circulate a metal-working liquid (often referred to as a “coolant”) during metal forming processes to remove heat generated and to filter it continuously to remove contaminants from the metal-working process. Over a period of time, the metal-working liquid will become increasingly contaminated with metal fines, tramp oil and other contaminants, some of which may be soaps that are formed from coolant chemical agent reaction with metal fines. At some point, the level of contamination may have a detrimental effect on the process, the equipment and the qualities of the metal objects being formed. At this stage, the metal-working liquid must be discarded and replaced, or it may be treated to remove the contaminants and re-used.
In order to maintain a continuously operating metal forming process, it is desirable to continuously treat the metal-working liquid for contaminants rather than to replace the liquid at intervals with batches of new or recycled metal-working liquid. Batch-wise replacement has the disadvantage that contaminant levels are low at the outset and increase over time until the liquid is replaced with a fresh batch. Accordingly, contaminant levels fluctuate from a low level, when the metal-working liquid is fresh, to a higher level at the point of liquid replacement. This cycling of contaminant level may have a deleterious effect on quality of the formed metal objects.